Technician Class 2018-2022: Pass Your Amateur Radio Technician Class Test - The Easy Way (EasyWayHamBooks Book 6) by Craig Buck K4IA & Buck K4IA

Author:Craig Buck K4IA & Buck K4IA [K4IA, Craig Buck]
Language: eng
Format: azw3
Published: 2018-02-12T00:00:00+00:00

CLEAN UP THE SIGNAL

You’ll know a bad signal when you hear it. You can tell from the chirpy, raspy sounding CW or over-driven, over-processed or garbled audio.

Too high a microphone gain and the output signal may become distorted . It is the same as shouting into the microphone. Don’t overdrive!

On FM, the amount of deviation is determined by the amplitude (loudness). If you are told you are over-deviating, move away from the microphone. You are too loud and your signal is too wide.

If you are told your transmissions are breaking up on voice peaks, you are talking too loudly. You are over-deviating, over-driving your transmitter.

A high-pitched whine in a mobile transceiver that varies with speed is usually the car’s alternator.

Since the noise is in your transmitter, you won’t hear it, but the person you’re talking to might comment. The cure is to connect your radio directly to the battery. Two things happen. First, you have less chance of being tied into a circuit with noise. Second, the battery acts as a huge filter capacitor.

There is nothing wrong with asking for or giving a critical signal report. Everyone wants to sound good and no one wants to be a “lid.” [12]

Sometimes, RF can get into the audio and be rebroadcast. That is RF feedback. A symptom of RF feedback is reports of garbled, distorted or unintelligible transmissions . Poor grounding or being close to your antenna can cause feedback.

Shielded wire prevents coupling of unwanted signals to or from the wire. Hint: A shield prevents coupling.

RF can get into your microphone cable, power cable or cables connected to the computer. To cure distorted audio caused by RF current on the shield of a microphone cable use a ferrite choke. Ferrite is a mixture of ceramic and metal that increases the effectiveness of a coil to resist the passage of RF. A few turns of your cable through a ferrite choke may solve your problem. Hint: A ferrite choke chokes off the RF.

To reduce or eliminate interference to a nearby telephone put an RF filter on the telephone. The phone line is acting as an antenna, and you need to choke off the RF with an RF filter. Hint: Filter RF with a filter.

The first step to resolve cable TV interference is to be sure all the connectors are installed properly. Loose connectors break the shield and allow interference to enter or exit. Tighten them down and make sure any cable that is not connected has a terminating plug. That is a small cap that screws on the unused end of a TV cable.

Radio frequency interference may be caused by Fundamental overload

Harmonics

Spurious emissions

All choices are correct

Hint: Lots of things cause interference. All are correct

An AM/FM radio might receive amateur radio transmissions because the receiver is unable to reject strong signals outside the AM or FM band. That is an example of fundamental overload. The amateur radio signal is so strong; it overwhelms the AM/FM radio.

To reduce the overload of a non-amateur radio or TV, block the amateur signal with a filter on the antenna input of the receiver .

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